This invention relates to a vehicle wheel and especially to a bicycle wheel having a rim section, a plurality of spoke sections and a hub section.
In recent years, participation in competitive cycling has increased dramatically and has created a demand for greater performance characteristics from cycling equipment. It is generally acknowledged that reduced aerodynamic drag, lower weight, increased rider comfort, lower maintenance and reduced cost are goals to consider when attempting to enhance the performance of bicycle equipment.
Conventional bicycle wheels are typically constructed using 28 or more individual wire spokes. Each of these spokes must continually break the wind as the wheel rotates, creating aerodynamic drag. An attempt to overcome some of this aerodynamic drag has been to construct the bicycle wheel as a solid disc. Although these disc wheels reduce the aerodynamic drag, rider stability and safety are significantly compromised. If prevailing wind patterns have any component perpendicular to the riders direction of travel, as is most often the case, the disc wheel acts as a sail resulting in a potentially dangerous instability problem. More recently, several manufacturers have introduced one-piece spoke wheels constructed from fiber reinforced plastic. These wheels attempt to reduce aerodynamic drag by reducing the number of individual spokes to three or five. However, in an effort to maintain lateral rigidity, these wheels utilize additional material in construction and weigh significantly more than a conventional wheel of comparable size. Additionally, the manufacturing processes required to produce these plastic spoke wheels are quite complex. Fabrication involves careful wrapping of fiber reinforcement cloth around a foam armature or plastic bladder, placing this assembly within a mold, together with uncured resin, and applying heat and pressure to the mold to cure the resin. This process is very labor intensive and requires highly skilled production personnel. Also, the disc type wheels and the plastic spoke wheels have been described as lacking the shock absorption and resiliency of conventional wheels, resulting in a more uncomfortable ride. These disc type wheels and plastic spoke wheels act to support a load on the axle through compression of the spoke or disc sector between the hub and the ground resulting in excessive rigidity. Conventional wheels support this load through tension of the spokes above the hub. It is this tension loading which gives the conventional wheel its resilient feel.
U.S. Pat. No. 5,104,199 represents an improvement over the foregoing and describes a vehicle wheel including an annular rim, a central hub, a plurality of spoke portions running between the rim and hub, and two wheel portions integrally joined to each other and including the spoke portions. It is desirable to provide a still further improvement over this construction.
It is particularly desirable to provide an improved vehicle wheel, especially a bicycle wheel, that can be manufactured at a reasonable cost through a configuration that leads itself to simple manufacturing processes, fewer component parts and minimal raw material. It would be highly advantageous to provide such a bicycle wheel with low aerodynamic drag and limiting the number of individual spokes and minimizing the spoke frontal area in the direction of rotation.
It would be particularly advantageous to provide a bicycle wheel as aforesaid which enables one to utilize spokes that are predetermined along their longitudinal axis to create a static structure with tension elements (spokes) and compression elements (rim and hub shell).
It is a further objective to enable one to provide a vehicle wheel as aforesaid that is light weight by utilizing light weight, high strength materials and by reducing the volume of material required to produce a structurally sound product.
Further objects and advantages of the present invention will appear hereinbelow.